Tolerance of Treatment Subsequent to Front-Line Tositumomab/Iodine-131 Tositumomab in Patients With Follicular Lymphoma

Front-line treatment for previously untreated follicular B-cell lymphoma withthe iodine-131-labeled anti-CD20 antibody tositumomab (Bexxar) has beenreported to result in a 97% response rate and a 74% complete response rate.Although the median duration of response has not yet been reached with a medianfollow-up of 2.7 years, concerns have been raised over the tolerability ofsalvage treatments upon relapse of disease. We have reviewed the clinical courseof the 28 patients that have relapsed among the original group of 76 patientstreated with tositumomab/iodine-131 tositumomab as front-line therapy.

Of 28 relapsed patients (median age, 50 years [range: 28-60 years]), 22have received some form of treatment and 6 are being observed. For those whowere subsequently treated, the median time from tositumomab/iodine-131tositumomab treatment to salvage treatment was 321 days (range: 67-1,440 days)and the median time from relapse to treatment was 104 days (range: 3-775days). Seventeen patients received at least one chemotherapy regimen at somepoint, 12 received rituximab (Rituxan) either alone or in combination withchemotherapy, 8 received localized irradiation (one as the only subsequenttreatment), and 1 was retreated with tositumomab/iodine-131 tositumomab. Themedian number of total regimens received post-tositumomab/iodine-131tositumomab was 2.5 (range: 1-7).

Of the 17 patients who received chemotherapy, 8 were given 2 or more regimens(range: 2-5), including 4 patients who underwent stem cell transplants(2 autologous, 2 allogeneic). All four of these transplanted patients hadreceived at least three prior chemotherapy regimens. With only one exception, nopatient had treatment discontinued because of blood count intolerance due to ahypocellular marrow. No difficulties were encountered in stem cell mobilizationor engraftment posttransplant. No cases of myelodysplasia or acute myelogenousleukemia have been observed to date. There were no adverse effects beyond thoseexpected in patients treated with rituximab or local irradiation.

CONCLUSION: Front-line tositumomab/iodine-131 tositumomab therapy does notpreclude other treatment options, including those involving myelosuppressiveagents.